diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 869dcd74df..19fe720d9c 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1248,6 +1248,9 @@ spool_tuples(WindowAggState *winstate, int64 pos)
 	if (winstate->partition_spooled)
 		return;					/* whole partition done already */
 
+	if (winstate->status == WINDOWAGG_PASSTHROUGH)
+		pos = -1;
+
 	/*
 	 * If the tuplestore has spilled to disk, alternate reading and writing
 	 * becomes quite expensive due to frequent buffer flushes.  It's cheaper
@@ -1256,7 +1259,7 @@ spool_tuples(WindowAggState *winstate, int64 pos)
 	 * XXX this is a horrid kluge --- it'd be better to fix the performance
 	 * problem inside tuplestore.  FIXME
 	 */
-	if (!tuplestore_in_memory(winstate->buffer))
+	else if (!tuplestore_in_memory(winstate->buffer))
 		pos = -1;
 
 	outerPlan = outerPlanState(winstate);
@@ -1295,9 +1298,12 @@ spool_tuples(WindowAggState *winstate, int64 pos)
 			}
 		}
 
-		/* Still in partition, so save it into the tuplestore */
-		tuplestore_puttupleslot(winstate->buffer, outerslot);
-		winstate->spooled_rows++;
+		if (winstate->status == WINDOWAGG_RUN)
+		{
+			/* Still in partition, so save it into the tuplestore */
+			tuplestore_puttupleslot(winstate->buffer, outerslot);
+			winstate->spooled_rows++;
+		}
 	}
 
 	MemoryContextSwitchTo(oldcontext);